• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.256-263
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• 2010

A Crofer 22 APU mesh coated with a conductive ceramic material was developed as an alternative cathode current collector to Ag-based materials for solid oxide fuel cells. $(La_{0.80}Sr_{0.20})_{0.98}MnO_3$ (LSM) layer was deposited onto the Crofer mesh using a spray-coating technique, in an attempt to mitigate the degradation of electrical properties due to surface oxidation at high temperatures. The oxidation experiments at $800^{\circ}C$ in air indicated that the areaspecific resistance (ASR) of the LSM-coated Crofer mesh was strongly dependent on the wire diameter and the contact morphology between mesh and cell. In addition, the post-heat-treatment in $H_2/N_2$ resulted in a reduced thickness of Cr-containing oxide scales at the interface between Crofer mesh and LSM layer, leading to a decreased ASR.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.141-149
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• 2009

The Cu thin film material and process, which have been already used for metallization of CMOS(Complementary Metal Oxide Semiconductor), has been highlighted as the Cu metallization is introduced to the metallization process for giga - level memory devices. The recent progresses in the development of key elements in electrochemical processes like surface pretreatment or electrolyte composition are summarized in the paper, because the semiconductor metallization by electrochemical processes such as electrodeposition and electroless deposition controls the thickness of Cu film in a few nm scales. The technologies in electrodeposition and electroless deposition are described in the viewpoint of process compatibility between copper electrodeposition and damascene process, because a Cu metal line is fabricated from the Cu thin film. Silver metallization, which may be expected to be the next generation metallization material due to its lowest resistivity, is also introduced with its electrochemical fabrication methods.

• Journal of the Korean institute of surface engineering
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• v.37 no.6
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• pp.360-365
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• 2004

Ti$_3$SiC$_2$ material was synthesized via the powder metallurgical route, and oxidation tested between 900 and $1200^{\circ}C$ in air for up to 100 hr. The oxidation of $Ti_3$$SiC_2$ material resulted in the formation of $TiO_2$and $SiO_2$, accompanying the evolution of CO or $CO_2$ gases from the initial stage of oxidation. The oxidation resistance of $Ti_3$$SiC_2$ mainly owes the protectiveness of highly stoichiometric $SiO_2$. During the initial stage of oxidation, the dominant reaction was the inward transport of oxygen into the matrix. As the oxidation progressed, an outer $TiO_2$ layer and an inner ( $TiO_2$ + $SiO_2$) mixed layer formed. Between these layers and inside the oxide scale, numerous fine voids formed. Numerous, fine oxide grains formed at $900^{\circ}C$ developed into the outer coarse $TiO_2$ grains and an inner fine ($TiO_2$ + $SiO_2$) mixed grains at the higher temperatures. The oxidation resistance of$ Ti_3$SiC$_2$ progressively deteriorated as the oxidation temperature increased, forming thick scales above $1000^{\circ}C$. The outer coarse $TiO_2$ grains formed above $1100^{\circ}C$ grew rapidly mainly along (211).

• Journal of the Korean institute of surface engineering
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• v.51 no.2
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• pp.104-109
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• 2018

Fe-2 wt.%Ni alloys were fabricated by metal powder injection molding, and their oxidation behavior at $600-700^{\circ}C$ for 30 h in air was studied in order to find the effect of the small addition of Ni in the iron matrix on the high-temperature oxidation. Oxide scales that formed after oxidation consisted primarily of $Fe_2O_3$, where microscopic voids were scattered. Nickel was segregated initially at the scale/matrix interface, and later at the lower part of the $Fe_2O_3$ scale. At $600^{\circ}C$, Fe-2wt.%Ni alloys oxidized parabolically initially, and linearly after 15 h. At $650-700^{\circ}C$, they oxidized linearly from the initial period. Although Fe-2wt.%Ni alloys oxidized slower than pure iron, their oxidation rates were relatively fast.

• Journal of the Korean institute of surface engineering
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• v.46 no.2
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• pp.80-86
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• 2013

Magnesium alloys of AZ31 containing (0.5, 1, 1.5) wt.% of initially added CaO particles were cast in air, and their oxidation behavior was studied at $450-650^{\circ}C$ in air. The initially added CaO particles either decomposed to dissolve in the ${\alpha}$-Mg matrix or precipitated as $Al_2Ca$ along the grain boundaries of the matrix during casting. The ignition temperatures were $565.4^{\circ}C$ for AZ31, $608.6^{\circ}C$ for AZ31+0.5 wt.%CaO, and $689.7^{\circ}C$ for AZ31+1 wt.%CaO. No ignition occurred for AZ31+1.5 wt.%CaO up to $700^{\circ}C$, displaying good oxidation resistance. The CaO-rich oxide scales that formed on the surface of the AZ31+(0.5, 1, 1.5) wt.%CaO alloys improved the oxidation resistance of AZ31 alloys.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.833-841
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• 2005

The oxidation resistance and electrical conductivity of various commercial ferritic stainless steels including STS444 were tested in an air atmosphere at $700^{\circ}C$. Crofer22 developed specially for SOFC interconnect was also examined for the aim of comparing with the test results of STS444. Although STS444 exhibited higher oxidation resistance than Corfer22, the electrical conductivity of the scale formed on Crofer22 was higher, indicating that the resistivity of scale formed on Crofer22 is much lower than that of STS444. To gain a better understanding of the relation between oxidation behavior and electrical conductivity, the oxide scales formed on STS444 and Crofer22 were analyzed in terms of the structure, composition, and phase. Consequently, the influence of alloying elements on electrical conductivity of Fe-Cr alloys was discussed.

• Journal of Powder Materials
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• v.20 no.3
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• pp.174-179
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• 2013

The study on the fabrication of iron powder from forging scales using hydrogen gas has been conducted on the effect of hydrogen partial pressure, temperature, and reactive time. The mechanism for the reduction of iron oxides was proposed with various steps, and it was found that reduction pattern might be different depending on temperature. The iron content in the scale and reduction ratio of oxygen were both increased with increasing reactive time at 0.1atm of hydrogen partial pressure. On the other hand, for over 30 minutes at 0.5 atm of hydrogen partial pressure, the values were found to be almost same. In the long run, iron metallic powder was obtained with over 90% of iron content and an average size of its powder was observed to be about $100{\mu}m$.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.905-909
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• 2010

Magnetic beads (Dynabeads$^{(R)}$) embedded in ~1 micron size polystyrene beads bearing surface carboxylic acid groups were modified with aminobenzyl ethylenediaminetetraacetic acid (ABEDTA) to concentrate or separate metal ions using pH gradients on micro and nano scales. The immobilization of ABEDTA was achieved by amide formation. The presence of the metal chelating functional group in the fully deprotonated form was confirmed by FT-IR. The chelation efficiency of beads was tested by determining metal ions in supernatant using GFAAS when pH gradients from 3 to 7. Mixtures of Cu and Mg and of Cd and Mn (at 10 ng/mL of metal) were separated as the difference in formation constant with the functional group of ABEDTA. The separation was repeated twice with relative standard deviation of <18%. A polydimethylsiloxane (PDMS) microchip column packed with EDTA-coated magnetic beads was optimized to concentrate metal ion for practical applications by eluting a Cu solution of micro scale at pH 3.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.253-259
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• 2007

A new material tester has been developed to measure mechanical properties of thin film specimens at high temperature. It is useful for observing oxide film growth or local deformation on the surface, and for measuring creep strength. Main characteristics of the tester is as follows; First, high temperature is achieved by Joule heating generated by electricity passing through the specimen, which does not need to enclose the specimen by a furnace or a heating chamber. The exposed specimen enables one to observe the surface during the test. Because the overall size of the test rig is compact, the whole test rig can be placed in a chamber for environmental controlled tests. The loading device is from a level scales. Not only static load with fixed counter weight, but also variable load by moving counter weight controlled remotely can be applied for an ordinary creep test and creep-fatigue test, respectively. The detail of the construction, operation principle, and the specification are described. And also, an example of test result obtained using the creep tester is presented.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.246-254
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• 2022

The high-temperature oxidation behavior of Cr-Mo steel AISI 4115 in air at different temperatures (600, 850, 950℃) for 120 min was studied by mass gain analysis, phase analysis (optical microscopy, electron probe micro-analysis, x-ray diffraction) and hardness measurement of each iron oxide-phase. The oxidation scales that formed on oxidation process consisted outer layer (Hematite), middle layer (Magnetite) and the inner layer (Chromite). In the case of 850 and 950℃, the oxidation mass gain per unit area of AISI 4115 steel increased according to the logarithmic rate as atmospheric pressure increased. Especially, It has been observed that with an increase in the atmospheric pressure at 600℃, the oxidation mass gain per unit area changed from a linear to logarithmic relationship.